Abstract: A magnetron includes a cathode and vane type anode structure. The frequency of oscillation of a microwave output signal of the magnetron is tunable by means of a tuning member, which is in the form of an annular plate arranged adjacent resonant cavities of the magnetron. The frequency of oscillation is determined by the position of the tuning member relative to the resonant cavities. When it is wished to tune the magnetron output frequency a current is passed along a path defined by the tuning member. This causes axial forces to be exerted on the tuning member so that it moves. Since the current is arranged to pass through the tuning member itself, the device is particularly simple, no actuating mechanisms or drive coils, for example, being necessary.

Abstract: A radar system having a common antenna for transmitting and receiving signals conventionally includes a branch duplexer which is bulky and inconvenient.By using a waveguide section having an antenna port at one end and a receiver port at the other, and including a protection unit comprising p.i.n. diodes these difficulties are reduced. The diodes prevent transmitted energy from a magnetron reaching the receiver port but allow received energy, because of its lower amplitude, to pass.

Abstract: A resonant cavity device--particularly a magnetron oscillator--has a separate resonator coupled to a resonant cavity of the device. The separate resonator consists of a resonant transmission line within which are two multipactor discharge arrangements, one being positioned at a distance along a resonant transmission line which is approximately 3.lambda./4 from the end of the transmission line adjacent the cathode and the other of which is positioned at a distance along the resonant transmission line which is .lambda./4 from the same end of the transmission line. By controlling the multipactor discharges of the multipactor discharge devices appropriately three different frequencies of operation are available.

Abstract: The invention provides a magnetron of the strapped anode type having three strapping members each co-axial but at different diameters from the center of the anode block of the magnetron. The middle strapping member is connected to alternate vanes and the innermost and outermost strapping members are connected to the remaining ones of the anode vanes.

Abstract: A multipactor discharge tuned resonant cavity device, e.g. a magnetron, is irradiated with X-rays in order to assist the starting of the multipactor discharge. The X-rays are produced by electrons striking the surface of the magnetron anode.

Abstract: A multipactor discharge tuned resonant cavity device, e.g. a magnetron, is arranged with two multipactor discharge electrodes so that in a discharge condition a net current flows from one electrode to the other. The net current is used to create a self-bias voltage on one of the electrodes which affects the operating frequency of the device.